27 



formation of new cuts ; the erection of walls for the guidance of 

 tidal currents, and the shutting up of subsidiary channels. And 

 the third compartment is the " river proper," which is characterised 

 by the absence of all tidal influence, the improvement of which is 

 generally effected by means of dams erected in the bed of the river, 

 and forming stretches of canal communicating with each other by 

 means of locks in the dams. The practical remarks are confined to 

 the improvement of the tidal compartment only, which possesses 

 sufRcient importance to entitle it to form the subject of a distinct 

 comnmnication ; the prosperity of the ports of London, Bristol, New- 

 castle, Glasgow, and many other places, being intimately connected 

 with it. 



The author shews, that, owing to the smallness of the rivers of 

 this comparatively narrow country, they can be advantageously 

 navigated only while their waters are deepened by the influx of the 

 tide, and proposes, as the surest means of effecting improvement, 

 such works as produce an increase in the duration of tidal injluence. 



Instances of the success of these works are given. The rise is 

 the bed of the Tay from Newburgh to Perth (8'56 miles), in con- 

 sequence of works that have been executed, has been reduced from 

 four to two feet. The time occupied in the passage of the tidal 

 wave between these places has been decreased fifty minutes, and 

 the speed with which it travels increased 1§ 0/ a mile per hour. 

 The duration of flood-tide at Perth has been increased fifty minutes, 

 and the time during which the river at that place is uninfluenced by 

 the tide, has been decreased forty-five minutes. It is also calcu- 

 lated that an additional quantity of sea water, amounting, on an 

 average, to 760,560 tons, is propelled into, and again withdrawn 

 from, that part of the river extending above Newburgh every tide. 

 At the Rubble in Lancashire, similar benefits have resulted from 

 similar operations ; the tidal range at Preston having been in- 

 creased between three and four feet, and the propagation of tho 

 tidal wave accelerated about forty minutes. 



The following are the practical inferences which the author draws 

 from the facts brought forward : — 



First, That owing to the comparatively contracted country from 

 the draiif&ge of which our rivei's derive their supplies, it is chiefly 

 from increased! duration of tidal influence that we must expect im- 

 provement in tide navigation, tho regulation of the fresh water 

 stream being an operation of secondary importance, but not, on that 

 account, to be overlooked. 



